INVESTMENTS IN CONSUMER LOANS - Allowance for Loan Losses on Performing Consumer Loans, Held-for-Investment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Loans Receivable [Roll Forward]
UPB of Underlying Mortgages	$ 103,000,000
Consumer Portfolio Segment
Loans Receivable [Roll Forward]
UPB of Underlying Mortgages	14,200
Post-modification recorded investment	12,600
Performing Loans | Consumer Portfolio Segment
Loans Receivable [Roll Forward]
Collectively Evaluated, beginning balance	4,429	$ 2,441
Individually Impaired, beginning balance	1,676	997
Beginning balance	6,105	3,438
Provision (reversal) for loan losses	48,227	65,738
Provision for loan losses	(49,664)	(63,071)
Collectively Evaluated, ending balance	2,604	4,429
Individually Impaired, ending balance	2,064	1,676
Ending balance	4,668	6,105
Recovery of bad debts	9,000	10,800
Performing Loans | Collectively Evaluated | Consumer Portfolio Segment
Loans Receivable [Roll Forward]
Provision (reversal) for loan losses	47,839	65,059
Provision for loan losses	(49,664)	(63,071)
Performing Loans | Individually Impaired | Consumer Portfolio Segment
Loans Receivable [Roll Forward]
Provision (reversal) for loan losses	388	679
Provision for loan losses	$ 0	$ 0